Methods of forming markings on metal surfaces



Oct. 7, 1969 R. H. v. FARRELL 3,471,385

METHODS OF FORMING MARKINGS ON METAL SURFACES Filed Feb. 6. 1967 10 10b 0 J TRADE MA K I 100 I COUNTRY OF ORIGJN Fla.

lJulk-l ldlrvwimnmvm.

AT TO R NEY United States Patent 3,471,385 METHODS OF FORMING MARKINGS 0N METAL SURFACES Ronald H. V. Farrell, Didcot, England, assignor to Wilkinson Sword Limited, London, England, a British company Filed Feb. 6, 1967, Ser. No. 614,105 Claims priority, application Great Britain, Feb. 11, 1966, 6,064/ 66 Int. Cl. C23b 3/02 US. Cl. 204-143 2 Claims ABSTRACT OF THE DISCLOSURE The invention provides a method of forming a desired permanent marking on a metal surface comprising applying a coating to a portion of the surface corresponding to the desired marking and, thereafter, subjecting the metal surface to electrolytic dissolution, whereby the amount of metal removed from the coated portion of the surface is different from the amount of metal removed from the remainder of the surface.

This invention relates to the formation of permanent markings, such as identification markings, on metal surfaces.

An object of the invention is to provide a method of marking metal surfaces which cannot be satisfactorily or conveniently marked by conventional methods, for example by etching.

According to the present invention there is provided the method of forming a desired permanent marking on a metal surface comprising coating a portion of said surface corresponding to said desired marking and, thereafter, subjecting the metal surface to electrolytic dissolution, whereby the amount of metal removed from the coated portion of said surface is different from the amount of metal removed from the remainder of said surface.

The invention also provides the method of forming a permanent marking on a metal surface comprising applying to said surface a resist corresponding to the desired marking, the material used for said resist having a predetermined electrical resistance, and submitting said metal surface to electrolytic dissolution to remove a greater thickness of metal from the uncoated portion of the surface than from that covered by said resist.

The invention further provides an electrolytic cell for selective electrolytic dissolution from a metal member, comprising a rotatable anode with which said member is maintained in non-sliding contact.

The novel features of the present invention will be better understood from the following description of one method of applying identification markings, such as a trademark, source of origin, etc. to razor blades.

In the accompanying drawing:

FIGURE 1 is a plan view of razor blade strip with identification marking printed but not permanently formed, whilst FIGURE 2 is a plan view of an electrolytic cell in which the formation of the permanent marking is completed.

In brief, in this method which exemplifies the invention the identification markings are printed on the razor blades and the razor blades are subsequently made anodic in an electrolytic cell. The material used for printing acts as a resist, but may have an electrical resistance such that current flows through the printing material to the metal beneath, such current being less than the current "ice which flows to the remainder of the surface of each razor blade. Irrespective of the exact mechanism the printing is such as to result in differential removal of metal whilst a blade is in the electrolytic cell so that, when the blades are removed from the cell, areas to which the printing material was applied are of differing level from the remainder of the metal surface and the identification markings are produced in a clear and durable manner.

Referring now to FIGURE 1, this shows razor blade strip 10 which has been punched to form locating slots 10a and to shape the strip to correspond to the final form of the individual blades, the strip also having had cutting edges 10b provided, so that only transverse cropping is required to provide the individual razor blades. The strip bears resists corresponding to a trademark 10c and a source of origin 10a.

The resists may be applied to the blade strip in any convenient manner; for example by means of an offset printing machine using a metal stereo.

As explained above the function of the resists is to cause the portion of the metal surface of the strip covered by the resists to respond differently to electrolytic dissolution from portions of the metal surface which are not covered by resists. Any material may be used for the resists which will perform this function. Thus, the material may act to reduce the current which flows to the metal surface beneath the resists thereby resulting in differential removal of metal.

We have found that synthetic resins are suitable for such resists and amongst those which have been used are maleic, cresylic and phenolic resins as well as a styrene/ maleic anhydride copolymer. For convenience of application such resins may be applied as dispersions, the resin being subsequently cured by heat treatment. For the latter purpose, heating may be by any conventional method, such as by the use of industrial gas or electricity, a particular example of the latter being by induction heating.

Examples of commercially available materials are:

(1) An esterified rosin-maleic resin sold under the designation Crayvallac 510. This resin was prepared and used as a 40% dispersion in dipropylene glycol.

(2) A novolak cresylic resin sold under the designation Crayvallac 280. This resin was prepared and used as a 40% dispersion in dipropylene glycol.

(3) A phenolic resin containing 8% hexamine sold under the designation Kelrez CM 550. This resin was prepared and used as a 45% dispersion in dipropylene glycol. l

(4) A styrene/maleic anhydride copolymer sold under the designation Lytron 820. This resin was prepared and used as a 10% dispersion in dipropylene glycol.

The above resins were cured by heat treatment within the range 230 C. to 300 C. It will be appreciated that a suitable thickness of the resist is readily determined by simple trials and can vary widely with satisfactory results.

The subsequent subjection of the blade strip bearing the cured resists to electrolytic dissolution may be performed in any appropriate manner. One convenient way of doing so is by the use of an electrolytic cell of the form shown in FIGURE 2. On the other hand the strip could be cropped and the individual blades subjected to electrolytic action if desired.

Referring now to FIGURE 2, the electrolytic cell illustrated comprises an electrolyte-containing tank 11 having two anodes 12, 13 in the form of rotatable wheels and two fixed arcuate cathodes 14, 15, the cathode 14 being spaced a short distance from the periphery of anode 12 and the cathode 15 being spaced a short distance from the periphery of anode 13. The blade strip 10 enters the tank 11 through inlet guides 16, passes around a part of the periphery of the anode 12 with one major surface of the strip in contact therewith, next passes around a part of the periphery of the anode 13 and emerges from the tank 11 through outlet guides 17. Whilst the strip is in contact with anode 12 there will be electrolytic dissolution of metal from the exposed metal surface with greater, less or even zero dissolution from the areas covered by resist. When this portion of strip comes into contact with the anode 13 similar electrolytic dissolution occurs from the surface which was previously not acted upon because it was in direct contact with the peripheray surface of anode 12. Because the anodes 12 and 13 rotate there is non-sliding contact which maintains the strip at anodic potential without risk of arcing or scratching. At least the surface of the anodes 12 and 13 is preferably of a metal which polarizes when in the anodic state, for example titanium, tungsten, tantalum, niobium or zirconium.

If it is only required to mark one side of the strip only one anode need be used.

The treatment in the electrolytic cell may also be such as to polish the unmarked surface of the blades to give a pleasing finished appearance.

This type of electrolytic cell using one or more wheels is novel per se and part from use with the above described method of marking, it can also be used solely for polishing of strip or for the electroforming or electrofinishing of one or more cutting edges on a strip. For either of the latter purposes the general conditions of electroforming or electrofinishing would be as described in patent applications Ser. Nos. 450,718 now US. Patent No. 3,399,130, 522,668, and 536,054 assigned to the same assignees as is the present application. Particularly in the case of electrofinishing, the surface of the wheel in contact with the strip could have a contour adjacent the edge of the strip suitable for acting as a bafile with the edge of the strip with the objects described in the aforesaid patent applica tion Ser. No. 522,668. On the other hand, the exposed surface of the strip could be appropriately bafiled either by stationary baffles or by means of an insulated or inert strip bearing on the outer surface of the blade strip, that is the surface which is not in contact with the arcuate surface.

I claim:

1. The method of forming a desired permanent marking on the surface of a metal strip, comprising applying a resist, in the form of a synthetic resin, to

said surface in successive patterns along the strip, each pattern corresponding to said marking, curing the resin by heat treatment,

passing the said strip longitudinally through an electrolytic cell wherein said strip is in contact with a portion of the peripheral surface of at least one rotatable electrically conductive wheel which is maintained at anode potential, and

electrically energising a further electrode with cathode potential, the further electrode being of arcuate shape and extending around, and spaced from, the said portion of the peripheral surface of the Wheel so as to subject the metal surface to electrolytic dissolution as it passes through the electrolytic cell whereby a greater thickness of metal is removed from the uncoated portion of the surface than from that covered by the said resist.

2. The method according to claim 1, wherein two rotatable electrically conductive wheels are provided, one surface of the strip contacting a peripheral portion of one wheel and the other surface of the strip contacting a peripheral portion of the other wheel, both wheels being maintained at anode potential and a respective arcuate electrode being arranged to extend around each said peripheral portion and being maintained at cathode potential.

References Cited UNITED STATES PATENTS 3,386,901 6/1968 Young 204-143 3,374,159 3/1968 Poodle 204-143 3,271,282 9/1966 Borth 204 143 2,999,771 9/1961 Gaynes 117-5.5 2,969,732 1/1961 Kendall 204-143 2,725,352 11/1955 Strobel 204-28 2,708,181 5/1955 Holmes et al. 204-28 2,610,120 9/1952 Minsk et a1 -7 1,942,025 1/1934 Frost 204-28 JOHN H. MACK, Primary Examiner SIDNEY S. KANTER, Assistant Examiner US. Cl. X.R. 204-206, 224 

